Automobile drag coefficient

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Barrier coefficient is a common measure in automotive design as it relates to aerodynamics. Drag is a force that functions parallel to and aligns with the airflow. The drag coefficient of the car affects the way the car passes through the surrounding air. When car companies design new vehicles they consider the car block coefficient in addition to other performance characteristics. Aerodynamic drag increases with the square of speed; therefore it becomes very important at higher speeds. Reducing the drag coefficient in the car improves the performance of the vehicle as it relates to the speed and fuel efficiency. There are many different ways to reduce vehicle barriers. A common way to measure vehicle barriers is through drag areas.

Video Automobile drag coefficient

Reduce drag

Reduced barriers in road vehicles have resulted in increased peak speed and vehicle fuel efficiency, as well as many other performance characteristics, such as handling and acceleration. The two main factors that impact the drag are the vehicle frontal area and the barrier coefficient. The drag coefficient is a unit-less value that indicates how many objects resist movement through liquids such as water or air. A potential complication for changing aerodynamic vehicles is that it can cause the vehicle to be too much lifted. Lift is an aerodynamic force that flows perpendicular to the airflow around the vehicle body. Too much lift can cause the vehicle to lose road traction which can be very unsafe. Lowering the coefficient of resistance comes from simplifying the vehicle's exterior body. Streamlining the body requires assumptions about the surrounding air velocity and the use of vehicle characteristics.

For high speed applications near or above the speed of sound, the Sears-Haack body, is the ideal form that minimizes drag waves, which are barriers associated with supersonic shock waves. This form consists essentially of an elongated tube with a pointy tip.

Maps Automobile drag coefficient

Deletion

Removal of parts on the vehicle is an easy way for designers and vehicle owners to reduce vehicle parasitic and frontal barriers with little cost and effort. Removal can be as simple as removing aftermarket parts, or parts that have been installed on the vehicle after production, or having to modify and remove the OEM parts, meaning any part of the vehicle originally made on the vehicle. Most sports car production and high efficiency vehicles are becoming standard with many of these removals in order to compete in the automotive and racecourse markets, while others prefer to maintain the drag-improving aspects of this vehicle for their visual aspect, or to customize it using a customer base they.

Roof rack

The roof rack is a common feature of many SUVs and station wagons. While roof racks are very useful in carrying extra storage on the vehicle, they also increase the frontal area of ​​the vehicle and increase the drag coefficient. This is because the air flows over the vehicle, following the fine lines of the hood and windshield, then collides with the roof rack and causes turbulence. The removal of this section has led to improved fuel efficiency in some studies.

Mud flap

Mudflaps are now rarely specified as standard on production cars because they interfere with the flow of clean air around the vehicle. For larger vehicles such as trucks, mud flaps are still important to control their sprays, and by 2010 new versions of mud flaps were introduced which have been shown to create fewer aerodynamic obstacles than standard mud flaps.

Rear spoiler

The rear spoiler is usually standard in most sports vehicles and resembles the wing shape that is lifted at the rear of the vehicle. The main purpose of the rear spoiler in vehicle design is to counter the lift, thereby increasing the stability at higher speeds. To achieve the lowest drag possible, air should flow around the body of a lean vehicle without coming in contact with the area of ​​possible turbulence. Rear spoiler design that protrudes from the rear deck cover will increase downforce, reducing lift at high speed while incurring drag penalties. Flat spoilers, perhaps a slight downward tilt can reduce turbulence and thereby reduce drag coefficient. Some cars now have a rear spoiler that can be adjusted automatically, so at lower speeds, the effect on drag is reduced when the benefits of reduced lifting are not required.

Mirror side

Side mirrors increase the frontal area of ​​the vehicle and increase the drag coefficient as they stand out from the side of the vehicle. To reduce the impact of the rearview mirror on dragging vehicles, the rearview mirror can be replaced with smaller mirrors or mirrors of different shapes. Some concept cars in 2010 replace the mirror with a small camera but this option is not common for production cars because most countries require side glass.

Radio antenna

Although they do not have the greatest impact on drag coefficients due to their small size, radio antennas normally found protruding from the front of the vehicle can be relocated and changed in design to remove the car from this additional drag. The most common replacement for a standard car antenna is the shark fin antenna found in most high efficiency vehicles.

Windscreen Wiper

The effects of windshield wipers on vehicle airflow vary between vehicles; However, they are often eliminated from race vehicles and high efficiency concepts to keep the smallest drag coefficient possible. A more common option is to replace windscreen wipers with low profile wipers, or simply remove windshield wipers on the passenger side of the vehicle, and even make deflectors to bend air up and through the wipers.

Another alternative is to equip a vehicle with a single wiper placed in the center of the windshield, allowing it to cover both sides of the windshield. This reduces the amount of drag by reducing the frontal area of ​​the blade. While such applications can be useful for racing, for most of these road vehicles will result in minimal improvements in overall barrier reduction.

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Fabrication

The application of new parts and concepts into vehicle design is easier to incorporate when in the design phase of the vehicle, rather than in the aftermarket (automotive parts), however, the fabrication of these parts helps in simplifying the vehicle and can help greatly reduce vehicle barriers. Most vehicles with very low drag coefficients, such as race cars and high efficiency concept cars, apply these ideas to their designs.

Wheel cover

When air flows around the wheel well it will be disturbed by the rim of the vehicle and form a turbulence area around the wheel. In order for air to flow more smoothly around the wheel properly, a smooth wheel cover is often applied. The smooth wheel cover is a hub cap with no holes in it for air to pass through. This design reduces obstacles; however, it can cause the brakes to heat up faster because the cover prevents airflow around the brake system. As a result, these modifications are more often seen in vehicles with higher efficiency than sports cars or racing vehicles.

Air curtain

The air curtain diverts the airflow from the slot in the body and guides it toward the outer edge of the wheel well.

Partial grid block

The front grille of the vehicle is used to direct air directly into the engine compartment. In a sleek design, air flows around the vehicle rather than through; However, the vehicle grille switches the airflow from all vehicles to the vehicle, which then increases the barriers. To reduce this impact, a block grille is often used. The grille block partially covers, or entirely, the vehicle's front grille. In most high efficiency models or on vehicles with low drag coefficient, very small grids will already be built into vehicle design, eliminating the need for grating blocks. The grille in most of the production vehicles is generally designed to maximize airflow into the engine compartment so as not to overheat. This design can really make too much airflow into the engine compartment, prevent it from warming up in a timely manner, and in such cases, the grid blocks are used to improve engine performance and reduce vehicle constraints simultaneously.

Under the tray

The bottom of the vehicle often traps air in various places and adds turbulence around the vehicle. In most racing vehicles this is eliminated by covering the entire underside of the vehicle in what is called a tray below. This tray prevents air from getting trapped under the vehicle and reduces obstacles.

Modified front bumper

The front bumper is the first part of the vehicle that air should flow around. Therefore, it plays an important role in reducing barriers. Front air dams are often used that extend from the very front of the vehicle to the bottom of the vehicle. This is done to direct the airflow around and above the vehicle rather than allowing air to travel underneath. Contoured deflectors, or tire spats, are often made as part of the front bumper to direct the airflow around the tires without increasing to the outflow.

Boattails and Kammbacks

A boattail can greatly reduce the total vehicle drag. Boattails creates a teardrop shape that will give the vehicle a sleeker profile, reducing the occurrence of obstacles that encourage flow separation. Kammback is a truncated boattail. This is made as an extension of the rear of the vehicle, moving the back of the rear with a slight incline towards the car bumper. This can reduce drag as well but the boattail will reduce the drag of more vehicles. Nonetheless, for practical and stylistic reasons, kammbacks are more often seen in racing, high-efficiency vehicles, and trucks.

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Typical drag coefficient

The average modern car achieves a drag coefficient between 0.25 and 0.3. SUVs, with the usual box shapes, usually reach C d = 0.35-0.45. The coefficient of resistance of a vehicle is influenced by the vehicle body shape. Various other characteristics affect the drag coefficient as well, and be taken into account in these examples. Some sports cars have a very high drag coefficient, but this is to offset the amount of lift generated vehicles, while others use aerodynamics to their advantage to gain speed and have a lower drag coefficient.

Some examples of C d follow. The numbers given are generally for the basic model. Some "high performance" models may in fact have higher drag, due to wider tires, extra spoilers and larger cooling systems since many basic/low power models have half-size radiators with the remaining areas put out to reduce cooling and engine resistance.

The position of C d of the given vehicle will vary depending on the wind tunnel be measured. Variations up to 5% have been documented and variations in test techniques and analysis can also make a difference. So if the same vehicle with drag coefficient C d = 0 , 30 measured in different tunnels it could be anywhere from C d =0.285 to C d = 0.315.

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Drag the area

While designers pay attention to the overall shape of the car, they also remember that reducing the frontal area of ​​the form helps reduce barriers. Products of drag coefficients and drag areas - represented as C d A (or C _x A ), multiplication of C d value by area.

The term drag area is derived from aerodynamics, where it is the product of some reference region (such as cross-sectional area, total surface area, or similar) and the barrier coefficient. In 2003, Car and Driver magazine adopted this metric as a more intuitive way to compare the aerodynamic efficiency of various cars.

Gaya yang diperlukan untuk mengatasi hambatan adalah: ${\ displaystyle {\ tfrac {1} {2}} \ kali {\ text {air density}} \ kali {\ text {drag coefficient}} \ times {\ text {reference area}} \ times {\ text {speed}} ^ {2}}  ÂÂ$ Oleh karena itu: ${\ displaystyle {\ tfrac {1} {2}} \ kali {\ text {air density}} \ kali {\ mathbf {\ text {drag area}}} \ kali {\ text {speed}} ^ {2}}  ÂÂ$ Di mana koefisien hambatan dan area referensi telah diciutkan ke dalam istilah area seret. Hal ini memungkinkan estimasi langsung dari gaya drag pada kecepatan tertentu untuk setiap kendaraan yang hanya area drag yang diketahui dan karena itu perbandingan lebih mudah.

As the C d A area is the fundamental value that determines the power required for the given voyage speed it is a critical parameter for fuel consumption with a fixed speed. This relationship also allows for estimates of new high speed cars with tuned engines,

${\ displaystyle {\ text {estimated top speed}} = {\ text {highest original speed}} \ times {\ sqrt [{3}] {\ frac {\ text {new power}} {\ text {original power}}}}}$

Atau daya yang diperlukan untuk target kecepatan tertinggi,

${\ displaystyle {\ text {power required}} = {\ teks {kekuatan asli}} \ times \ left ({\ frac {\ text {target speed}} {\ teks {kecepatan asli}}} \ kanan) ^ {3}}  ÂÂ$

The average full-sized passenger car has a drag area of ​​about 8.50 m² (0.790 m ² ). The reported drag areas range from 1999 Honda Insight at 5.1 sq ft (0.47 m ² ) to Hummer H2 2003 at 26.5 sq ft (2.46 m ² ). The bike drag area (and the rider) is also in the range of 6.5-7.5 sqÃ, ft (0.60-0.70 m ² ).

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See also

• Automotive aerodynamics
• Drag (physics)
• Drag equation
• Paul Jaray

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Note

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References

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External links

• Further 500 drag coefficients
• Increase Aerodynamics to Improve Fuel Economy
• Tel Aviv University reduced the truck's obstacles by 10%
• Simple scrolling test to measure Cd and Crr for cars and bicycles

Source of the article : Wikipedia